When you buy from Steam, the product key is automatically linked to your account. If you buy from a third-party store, you will be emailed an activation code.

Navigate to the top menu and select "Games" or click "+ Add a Game" in the bottom-left corner. Step 3: Select "Activate a Product on Steam..."

Ensure you are matching the correct format. A Steam key has three groups of five characters, while the legacy game uses five groups of five characters.

Purchase the game from (often $5 during sales), the official SCS Software website, or an authorized reseller like Humble Bundle. This gives you a real, permanent product key linked to your account.